Water and Wastewater Terms Beginning S

A B C D E F G H I J K L M N O P Q R S T U V W Y Z

sludge volume index (SVI)

A calculation that indicates the tendency of activated sludge solids (aerated solids) to thicken or to become concentrated during the sedimentation/thickening process. SVI is determined in the following manner: allow a mixed liquor sample from the aeration basin to settle for 30 minutes, measure the suspended solids concentration for a sample of the same mixed liquor, and calculate the SVI by dividing the measured (or observed) wet volume (mililiters/liter) of the settled sludge by the dry weight concentration of MLSS in grams/liter.

 

SVI [mL/g] = ((settled sludge volume/sample volume [mL/L]) / (suspended solids concentration [mg/L])) X (1000 mg / g)